1. the theory that the response made by an individual to a stimulus that permits behavioral control involves two stages: (a) a decision as to whether or not to respond and (b) a choice between alternative responses.

2. in theories of memory, the operation of two different cognitive processes (e.g., recollection and familiarity) in recognition memory.

3. a decision-making theory stating that judgment and reasoning involve two separate processes: intuitive decision making and rational decision making. See System 1. [proposed by Daniel Kahneman and Amos Tversky]